Conventional tumbler locks include a key-operated plug rotatably mounted in a cylindrical shell. The plug includes a plurality of combinating tumblers, typically disc tumblers, which are biased to extend into the shell to prevent rotation of the plug in the locked position. When a properly bitted key is inserted into the plug keyway, and hence through slots in the combinating tumbler, the combinating tumblers are retracted from the shell forming an unlocked position to allow the plug to rotate.
It often is necessary to replace the plug to change the keys which will operate the locks, for security purposes, such as changing tenants or employees. One type of removable plug is disclosed in U.S. Pat. No. 4,398,405 (3 405). The '405 patent allows the plugs to be removed from a lock and changed, however, the combinating tumbler construction is such that the combinating tumblers themselves are not removable. The combinating tumblers are force fit into the plugs during assembly of the plugs. Then the keys in the individual plugs are not changeable. Further, the force fitting of the combinating tumbler during assembly can cause burrs on the tumbler or plug and/or crimping of the combinating tumblers causing the plug to be inoperable or to fail during operation from breakage or jamming.
It thus would be desirable to provide a combinating tumbler plug, which does not require force fitting of the combinating tumblers during assembly and in which the combinating tumblers easily can be removed for replacement and to change keys which will operate the plug.